1. Field of the Invention
This invention relates generally to tools and more particularly to a novel open chamber gas powered tool and a gas generating charge for the tool. The invention relates also to a novel method of fabricating the charge and packaging the charge in a magazine for feeding charges to the tool.
1. Prior Art
As will appear from the ensuing description, the tool and charge of the invention may be adapted to perform various work operations. The particular tool described is a fastener driving tool for driving fasteners, such as nails, studs, and the like, into a workpiece.
Propellant gas powered fastener driving tools are known in the art. One class of such tools fires fasteners into a workpiece at high velocity in much the same way as a gun fires a bullet into a target. Many tools of this class constitute dangerous lethal weapons in that they lack safety means to prevent their firing except when engaged with a workpiece and/or penetration of the fired fasteners completely through the workpiece. There are, of course, tools of this class on the market which do embody safety means for avoiding both of the above stated hazards.
Another disadvantage of many tools of the character described resides in the fact that they embody a closed chamber breech mechanism, that is a breech mechanism having a closed bore-like firing chamber which is completely surrounded circumferentially by a wall. The charges or ammunition to be fired in these tools must be inserted axially into the firing chamber through its breech end and the spent case of each fired charge must be extracted axially through the breech end of the firing chamber. Because of this method of introducing the charges into and extracting the spent cases of the charges from the firing chamber, most tools of this kind are single shot devices which must be reloaded by hand after each shot, thereby rendering use of such tools quite tedious, time consuming, and costly.
Another class of tools which may be used for driving fasteners as well as for other applications are gas powered percussion tools. These tools have a breech mechanism for firing gas generating charges, and a plunger which is propelled through a working stroke by the gas generated by each fired charge. The plunger working stroke may be utilized to drive a fastener, deliver an impact to a workpiece, or perform some other work operation. Examples of tools of this latter class are described in my prior Pat. No. 3,514,026 as well as in U.S. Pat. No. 3,283,657, and British Pat. Nos. 1,036,224 and 1,074,195.
The percussion tool described in my prior U.S. Pat. No. 3,514,026 is an open chamber tool having a forewardly opening cylinder or barrel containing a plunger and an open chamber breech mechanism at the rear end of the barrel in which propellant charges are fired to drive the plunger through a forward working stroke in the barrel. A spring returns the plunger to its normal rearward position in the barrel following each working stroke. The propellant charges which are used in the tool are essentially conventional open chamber ammunition cartridges of the kind described in my prior patents referenced in the above identified tool U.S. Pat. No. 3,514,026 except that the percussion tool charges lack a projectile or bullet. Thus, the propellant charges for my patented percussion tool comprise a plastic open chamber cartridge case or jacket containing a propellant and having a rear end wall. Mounted in this end wall is a primer which is detonated by a trigger actuated hammer on the tool to ignite the propellant and thereby generate high pressure propellant gas for operating the tool.
My patented percussion tool has two distinct advantages. First, relative to its use for driving fasteners, the tool effectively pushes the fasteners into a workpiece with a relatively large force but a relatively low velocity, thereby vertually eliminating the safety hazards associated with the prior high velocity fastener driving tools. Secondly, the open chamber breech permits a relatively simple and low cost tool with a repeater application which is uniquely adapted to a wide variety of high production rate uses, such as driving fasteners in the building construction trade.